1. Field of the Invention
The present invention relates to an instrumentarium and a method for implanting a cruciate ligament replacement in a knee joint.
Operations by which a cruciate ligament replacement is implanted in a knee joint are generally known in the art. Such operations become necessary in cases where the cruciate ligament in the knee is broken or has been heavily damaged in some other way. Today, one preferably uses endogenous materials as cruciate ligament replacements. Especially the patellar tendon or the semitendinosus tendon have proved to be suitable for use as a required cruciate ligament replacement.
2. Related Prior Art
A method and an instrumentarium for restoring the anterior cruciate ligament using one of such tendons as a cruciate ligament replacement has been known from EP-A-0 440 991.
If in the case of this known method the semitendinosus tendon is to be used as a substitute for the cruciate ligament, the tendon is initially removed with the aid of a tendon cutter, and is then cut to different segments or sections. Some of these segments are folded over in the form of a loop so that double sections are obtained. The individual segments and/or the double segments are then once more placed one beside the other, and their ends are connected by suture threads. The tendon bundle so obtained then forms the replacement for the cruciate ligament.
The cruciate ligament replacement is then fixed between the distal end of the femur and the proximal end of the tibia. To this end, one initially drills a through-bore in the proximal end of the tibia, and a blind bore or closed tunnel in the distal end of the femur, whereafter the ends of the cruciate ligament replacement are inserted into, and fixed in, the two bores, respectively.
Fixing the cruciate ligament replacement in the through-bore of the tibia is effected with the aid of a screw, according to EP-A-0 440 991. In contrast, for fixing the cruciate ligament replacement in the blind bore of the femur, it is stretched by means of suture threads, that are guided through a thin drilled passing channel forming an extension of the blind bore, and a button-like plate applied against an outer face of the femur opposite the blind bore.
If the operation has been successful, this purely mechanical method of fixing the cruciate ligament replacement in the two bores is reinforced, in the course of time, by the cruciate ligament replacement taking adhesion to the surrounding bone material. This adhesion then finally guarantees a durable and reliable hold for the cruciate ligament replacement in the knee.
However, it has been found that when implanted by that method the cruciate ligament replacement does not in all cases grow to the surrounding bone material as desired. This may happen in particular when the cruciate ligament replacement is retained too loosely in the receiving bore. For, in this case the cruciate ligament replacement tends to move with every, even very slight, movement of the knee so that an initial adhesion, that may have formed, is easily broken up again. Another, likewise frequently encountered cause for such difficulties lies in the fact that the cruciate ligament replacement as such has too little contact with the surrounding bone material.
This latter situation may arise in particular when the cruciate ligament replacement, as has been mentioned before, consists of segments folded over in the form of a loop. This is so because the maximum bending radii make the end of the cruciate ligament replacement, i.e. the area of the loop, larger than the area immediately beneath the latter. When the loop is then to be introduced into the blind bore of the femur in the usual way, it is the width of the loop that determines the size and/or the diameter of the blind bore. And this in turn leads to the situation that clear spaces remain below the loop between the cruciate ligament replacement and the walls of the blind bore. Due to such clear spaces, there is no contact between the cruciate ligament replacement and the surrounding bone material at these points, whereby any adhesion is rendered difficult or may even be prevented.
It is, therefore, an object of the present invention that the before-mentioned difficulties should be avoided. It is a further object of the invention to provide an instrumentarium for implanting a cruciate ligament replacement in a knee joint.